************************************************************** GVP/USGS Weekly Volcanic Activity Report 19-25 September 2007 http://www.volcano.si.edu/reports/usgs/ ************************************************************** New Activity/Unrest: | Augustine, USA | Ruapehu, New Zealand Ongoing Activity: | Arenal, Costa Rica | Chikurachki, Russia | Colima, México | Karymsky, Russia | Kilauea, USA | Pavlof, USA | Rabaul, Papua New Guinea | Semeru, Indonesia | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador | Ubinas, Perú New Activity/Unrest AUGUSTINE SW Alaska, USA 59.363°N, 153.43°W; summit elev. 1,252 m AVO increased the Volcanic Alert Level to Advisory and the Aviation Color Code to Yellow for Augustine on 22 September due to an increase in seismic activity below the summit over the previous week. During 22-25 September, the earthquakes were generally less than M 1 and were located at shallow depths beneath the summit. Geologic Summary. Augustine volcano, rising above Kamishak Bay in the southern Cook Inlet about 290 km SW of Anchorage, is the most active volcano of the eastern Aleutian arc. It consists of a complex of overlapping summit lava domes surrounded by an apron of volcaniclastic debris that descends to the sea on all sides. Few lava flows are exposed; the flanks consist mainly of debris-avalanche and pyroclastic-flow deposits formed by repeated collapse and regrowth of the volcano's summit. The latest episode of edifice collapse occurred during Augustine's largest historical eruption in 1883; subsequent dome growth has restored the volcano to a height comparable to that prior to 1883. The oldest dated volcanic rocks on Augustine are more than 40,000 years old. At least 11 large debris avalanches have reached the sea during the past 1800-2000 years, and five major pumiceous tephras have been erupted during this interval. Historical eruptions have typically consisted of explosive activity with emplacement of pumiceous pyroclastic-flow deposits followed by lava dome extrusion with associated block-and-ash flows. Source: Alaska Volcano Observatory http://www.avo.alaska.edu/activity/Augustine.php Augustine Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1103-01- RUAPEHU North Island, New Zealand 39.28°S, 175.57°E; summit elev. 2,779 m An eruption of Ruapehu that occurred on 25 September prompted GeoNet to raise the Alert level to 2 (on a scale of 0-5). Pilots reported that an eruption plume rose to an altitude below 4.6 km (15,000 ft) a.s.l. Further reports from ski field operators and the Eastern Ruapehu Lahar Alarm and Warning System (ERLAWS) indicated that lahars traveled down the Whakapapa ski field and possibly E in the Whangaehu river valley, and other areas. On 26 September, aerial observations revealed that the summit area was covered with ash and mud, mostly directed N and reached 2 km from the crater lake. Impact craters caused by falling blocks over 1 m in diameter were also evident. According to news articles, the eruption prompted evacuations at several ski lodges and caused train service to be temporarily suspended. A boulder crashed through the roof of a hut and injured one person. Geologic Summary. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes. The 110 cu km volcanic massif is elongated in a NNE-SSW direction and is surrounded by another 100 cu km ring plain of volcaniclastic debris. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flanks have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to river valleys below the volcano. Sources: New Zealand GeoNet Project http://www.geonet.org.nz/, Agence France-Presse http://news.yahoo.com/s/afp/20070925/sc_afp/nzealandvolcano_070925213824 Ruapehu Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0401-10= Ongoing Activity ARENAL Costa Rica 10.46°N, 84.70°W; summit elev. 1,657 m Based on initial observations from park visitors and resort personnel, OVSICORI-UNA reported that a pyroclastic flow from Arenal traveled W on 18 September. The event was recorded by a local seismic station. Based on field observations, a scientist from Instituto Costarricense de Electricidad (ICE) reported that multiple pyroclastic flows traveled S an approximate distance of 1 km on 18 September. Explosions occurred that occasionally produced ash. Small avalanches were noted and one larger avalanche on the S flank was incandescent. Avalanche activity continued on 19 September. Geologic Summary. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1,657-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. The earliest known eruptions of Arenal took place about 7,000 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. Arenal's most recent eruptive period began with a major explosive eruption in 1968. Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank. Sources: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/, Jorge Barquero Hernandez, Instituto Costarricense de Electricidad (ICE) http://www.ice.co.cr/ Arenal Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-033 CHIKURACHKI Kuril Islands, Russia 50.325°N, 155.458°E; summit elev. 1,816 m KVERT reported that explosions from Chikurachki produced ash plumes that were visible on satellite imagery and drifted SE during 18-19 September. Clouds obscured views of the summit during 15-17 and 20-21 September. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized scoria deposits covering the upper part of the young cone give it a distinctive red color. Lava flows from 1,816-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The more erosionally modified Tatarinov group of six volcanic centers is located immediately to the S of Chikurachki. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml Chikurachki Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-036= COLIMA Western México 19.514°N, 103.62°W; summit elev. 3,850 m During 19-23 September, steam and steam-and-ash plumes from Colima rose to altitudes of 4-4.9 km (13,100-16,100 ft) a.s.l. and drifted SW, W, and SE. Geologic Summary. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4,320 m high point of the complex) on the N and the historically active Volcán de Colima on the S. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the S, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth. Source: Gobierno del Estado de Colima http://www.colima-estado.gob.mx/2006/seguridad/indvolcan.php Colima Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-04= KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m KVERT reported that seismic activity at Karymsky was above background levels during 14-21 September. Observations of satellite imagery revealed that ash plumes drifted SE on 15 September and a thermal anomaly was present in the crater during 13-15 and 17-19 September. Based on seismic interpretation, ash plumes may have risen to an altitude of 3.3 km (10,800 ft) a.s.l. during 15-16 and 20 September. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Based on pilot reports, information from KEMSD, observations of satellite imagery, and observations in the Petropavlovsk-Kamchatsky Flight Information Region (FIR), the Tokyo VAAC reported that ash plumes rose to altitudes of 4.6 km (15,000 ft) a.s.l. on 21 September and 3.4 km (11,000 ft) a.s.l. on 25 September. Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html Karymsky Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m HVO reported that during 19-25 September fissure segment D from Kilauea's 21 July fissure eruption continued to feed an advancing 'a'a lava flow that occasionally overflowed its channel edges. Several of the lava flows that branched from the main channel continued to advance, widening and lengthening the flow field. A few small earthquakes were located beneath Halema'uma'u crater, the upper E rift zone, the S flank, and the lower SW rift zone during the reporting period. Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed by lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. The latest Kilauea eruption began in January 1983 along the E rift zone. This long-term ongoing eruption from Pu'u 'O'o-Kupaianaha has produced lava flows that have traveled 11-12 km from the vents to the sea, paving broad areas on the S flank of Kilauea and adding new land beyond the former coastline. Source: US Geological Survey Hawaiian Volcano Observatory http://volcano.wr.usgs.gov/hvostatus.php Kilauea Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01- PAVLOF Alaska, USA 55.42°N, 161.887°W; summit elev. 2,519 m On 19 September, a field crew confirmed that all eruptive activity from Pavlof ceased. AVO decreased the Volcanic Alert Level to Advisory and the Aviation Color Code to Yellow on 20 September due to a significant decrease of seismic activity during the previous week. Geologic Summary. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavolf, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing strombolian to vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption of Pavlof took place in 1911, at the end of a 5-year-long eruptive episode; a fissure opened on the northern flank of the volcano, ejecting large blocks and issuing lava flows. Source: Alaska Volcano Observatory http://www.avo.alaska.edu/ Pavlof Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1102-03- RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit elev. 688 m RVO reported that ash plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 1.2 km (3,900 ft) a.s.l. and drifted W and NW on 20 September. Ashfall was reported from areas downwind, including Rabaul Town. White vapor plumes containing a small amount of ash were emitted during 20-24 September. On 25 September, ash plumes rose to an altitude less than 1.7 km (5,600 ft) a.s.l. and drifted W. Roaring noises were heard. Ashfall was reported from areas downwind, including Namanula Hill. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city. Source: Herman Patia, Rabaul Volcano Observatory Rabaul Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14= SEMERU Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m Based on a pilot observation, the Darwin VAAC reported that an ash plume from Semeru rose to an altitude of 7.3 km (24,000 ft) a.s.l. on 22 September. Ash was not detected on satellite imagery. Geologic Summary. Semeru is the highest volcano on Java and one of its most active. The symmetrical stratovolcano rises abruptly to 3,676 m above coastal plains to the S and lies at the southern end of a volcanic massif extending N to the Tengger caldera. Semeru has been in almost continuous eruption since 1967. Frequent small-to-moderate Vulcanian eruptions have accompanied intermittent lava dome extrusion, and periodic pyroclastic flows and lahars have damaged villages below the volcano. A major secondary lahar on 14 May 1981 caused more than 250 deaths and damaged 16 villages. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html Semeru Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-30= SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev. 3,283 m KVERT reported that seismic activity at Shiveluch was above background levels during 14-21 September. During 14-15 and 17-20 September, avalanches occurred and ash plumes rose to altitudes of 3.5-5.5 km (11,500-18,000 ft) a.s.l. Observations of video data indicated that gas-and-ash plumes rose to an altitude of 3.3 km (10,800 ft) a.s.l. and drifted NE and E on 14 and 15 September. Gas-and-steam plumes were noted on 13, 18, and 19 September. A thermal anomaly was present in the crater on satellite imagery during the reporting period. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large horseshoe-shaped caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. During the 1990s, intermittent explosive eruptions took place from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml Shiveluch Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m MVO reported that during 19-25 September the lava dome at Soufrière Hills changed very little, based on visual observations. Seismic activity was very low and low-level rockfall activity continued. The Alert Level remained elevated at 4 (on a scale of 0-5). Geologic Summary. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the east, was formed during an eruption about 4000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption. Source: Montserrat Volcano Observatory http://www.mvo.ms/ Soufrière Hills Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05= ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m Data from deformation-monitoring instruments indicated that during 19-25 September lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. Clouds occasionally inhibited visual observations. Geologic Summary. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago, and has been the most active volcano in the Cascade Range during the Holocene. The modern edifice was constructed during the last 2,200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the N flank, and were witnessed by early settlers. Source: US Geological Survey Cascades Volcano Observatory http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html St. Helens Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05- TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m IG reported that ash and steam-and-ash plumes from Tungurahua rose to altitudes of 5.3-7 km (17,400-23,000 ft) a.s.l. during 19-20 and 22-24 September and drifted SW, W, and NW. Ashfall was reported in areas to the SW and W on 20, 23, and 24 September. Roaring and "cannon shot" noises were occasionally heard from multiple areas. On 22 and 23 September, incandescent material was ejected above the summit and blocks descended 300 m and 500 m down the flanks, respectively. On 23 September, explosions rattled windows in areas W and SW. Geologic Summary. The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador's capital city, and is one of Ecuador's most active volcanoes. Historical eruptions have been restricted to the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano. Source: Instituto Geofísico-Escuela Poltécnica Nacional http://www.igepn.edu.ec/ Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m Based on pilot reports, the Buenos Aires VAAC reported that an ash plume from Ubinas rose to altitudes of 5.5-6.4 km (18,000-21,000 ft) a.s.l. and drifted E on 12 and 20 September. Ash was not identified on satellite imagery. Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Peru. The upper slopes of the stratovolcano, composed primarily of Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include some of Holocene age. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor explosive eruptions. Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html Ubinas Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02= +++++++++++++++++++++++++++++++++++++ Sally Kuhn Sennert SI/USGS Weekly Volcanic Activity Report Editor Global Volcanism Program http://www.volcano.si.edu/reports/usgs/ Smithsonian Institution, National Museum of Natural History Department of Mineral Sciences, MRC-119 Washington, D.C., 20560 Phone: 202.633.1805 Fax: 202.357.2476 ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
